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Perkin Synthesis
The Perkin reaction is an organic reaction developed by English chemist William Henry Perkin in 1868 that is used to make cinnamic acids. It gives an α,β-unsaturated aromatic acid or α-substituted β-aryl acrylic acid by the aldol condensation of an aromatic aldehyde and an acid anhydride, in the presence of an alkali salt of the acid. The alkali salt acts as a base catalyst, and other bases can be used instead. Several reviews have been written. Reaction mechanism Clear from the reaction mechanism, the anhydride of aliphatic acid must contain at least 2 α-H for the reaction to occur. The above mechanism is not universally accepted, as several other versions exist, including decarboxylation without acetic group transfer.Bansal, Raj K. (1998) ''Organic Reaction Mechanisms'', Tata McGraw Hill, 3rd Edition , pp. 199–201, . Applications * Salicylaldehyde converted to coumarin using acetic anhydride with acetate as base. * cinnamic acid is prepared from benzaldehyde, a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
William Henry Perkin
Sir William Henry Perkin (12 March 1838 – 14 July 1907) was a British chemist and entrepreneur best known for his serendipitous discovery of the first commercial synthetic organic dye, mauveine, made from aniline. Though he failed in trying to synthesise quinine for the treatment of malaria, he became successful in the field of dyes after his first discovery at the age of 18. Perkin set up a factory to produce the dye industrially. Lee Blaszczyk, professor of business history at the University of Leeds, states, "By laying the foundation for the synthetic organic chemicals industry, Perkin helped to revolutionize the world of fashion." Early years William Perkin was born in the East End of London, the youngest of the seven children of George Perkin, a successful carpenter. His mother, Sarah, was of Scottish descent and moved to East London as a child.UXL Encyclopedia of World Biography (2003). Accessed 18 March 2008. He was baptized in the Anglican parish church of St ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Catalyst
Catalysis () is the increase in rate of a chemical reaction due to an added substance known as a catalyst (). Catalysts are not consumed by the reaction and remain unchanged after it. If the reaction is rapid and the catalyst recycles quickly, very small amounts of catalyst often suffice; mixing, surface area, and temperature are important factors in reaction rate. Catalysts generally react with one or more reactants to form intermediates that subsequently give the final reaction product, in the process of regenerating the catalyst. The rate increase occurs because the catalyst allows the reaction to occur by an alternative mechanism which may be much faster than the noncatalyzed mechanism. However the noncatalyzed mechanism does remain possible, so that the total rate (catalyzed plus noncatalyzed) can only increase in the presence of the catalyst and never decrease. Catalysis may be classified as either homogeneous, whose components are dispersed in the same phase (usual ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pechmann Condensation
The Pechmann condensation is a synthesis of Coumarin derivatives, coumarins, starting from a phenol and a carboxylic acid or ester containing a β-carbonyl group. The condensation is performed under acidic conditions. The mechanism involves an esterification/transesterification followed by attack of the activated carbonyl ortho to the oxygen to generate the new ring. The final step is a dehydration, as seen following an aldol condensation. It was discovered by the Germany, German chemist Hans von Pechmann . Mechanism To synthesize coumarin derivatives, β-ketoesters can be condensed with phenols under acidic conditions. In this case, a transesterification reaction occurs first with the formation of the phenol ester. This is then followed by ring closure, similar to Friedel–Crafts reaction#Acylation, Friedel-Crafts alkylation. Examples With simple phenols, the conditions are harsh, although yields may still be good. With highly activated phenols such as resorcinol, t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
